Adjustable-inclined bed knife



April 1966 H. R. SMITH ETAL 3,244,049

ADJ USTABLE-INGLINED BED KNIFE Filed June 17, 1964 INVENTOR.

HAROLD R. SM BY WALTER C. THY

ATTORNEYS United States Patent 3,244,049 ADJUSTABLE-INCLINED BED KNIFEHarold R. Smith, Georgetown, and Walter C. Thyng, Methuen, Mass.,assignors to Bolton-Emerson, Inc.,

Lawrence, Mass, a corporation of Massachusetts Fiied June 17, 1964, Ser.No. 375,703 7 Claims. (Cl. 83355) This invention relates to an improved,detachable, stationary, toothed bed knife of the type used inpelletizing machines, or the like.

Such pelletizing machines usually include a set of toothed fly knivesrotating on a fixed axis and a web supporting bed which feeds a webgenerally radially over the bed knife into the path of the fly knives.

The stationary toothed bed knife of such machines conventionallyincludes an upper face lying in a radial plane relative to the axis ofrotation of the fly knives, the forward upper portion of the upper facerequiring to be ground down occasionally to renew the forward upper,toothed cutting edge.

However, with each said grinding the forward upper cutting edge portionof the upper face is brought to a lower level below the radial plane andeventually the shelf, or recess, so formed fails to properly engage theteeth of the fly knives, the pellets are torn out of the advancing webrather than being severed therefrom and the web tends to flutter at thecut.

It is the principal object of this invention to provide a bed knife inwhich the advancing web is guided upwardly from a radial plane into thepath of the fly knives so that the cutting edge is initiallysubstantially above the radial plane. Thus the cutting edge portion ofthe upper face can be ground down for renewal many times before thecutting edge is lowered to the level of the radial plane and withoutcausing flutter.

Another object of the invention is to provide a pelletizing, toothed,bed knife having an upper face which inclines upwardly and forwardlyfrom the rearward edge to proximate the forward cutting edge, theforward portion of the upper face being horizontal and the mid width ofthe upper face being intersected by the plane of the web supporting bedof the machine. Flexible plastic webs, to be cut on the said bed knife,thus have their leading edges lifted to a level substantially above thenormal radial cutting plane but the leading edges are directedsubstantially radially of the fly knives in the actual cutting zone.

Other objects and advantages of the invention will be apparent from theclaims, the description of the drawing and from the drawing in which:

FIGURE 1 is a diagrammatic side elevation, in section, of the improvedbed knife of the invention in position in a typical pelietizing machine,and

FIGURE 2 is a fragmentary plan view of the bed knife shown in FIGURE 1.

In the drawing a typical pelletizing machine is illustrateddiagrammatically, there being the conventional bed 21, driven rolls 22and 23 forming a nip 24 for propelling a continuous web, or sheet, 25 ofthe material to be pelletized, the material usually being plastic. Flyknives 26 and 27 rotate in a cylindrical path, on a driven shaft 28,unidirectionally around the axis 29 of the shaft in the direction of thearrows. Concentric, circular dotted lines 31 and 32 illustrate the pathof the toothed cutting edges 33 and 34 of the fly knives and a dottedline 35 illustrates the plane of the upper face 36 of bed 21, projectedto the axis 29 in a plane radial to the path of the fiy knives.

The upper face of conventional toothed bed knives, and the toothedcutting edges thereof, usually -lie in the generally horizontal plane 35with the web such as 25 3,244,049 Patented Apr. 5, 1966 guided andsupported along the plane. As mentioned above, it will be apparent thatas soon as the cutting edges wear down, or are ground down, theeffective cutting edge of the bed knife will be below the radial plane35 and will drop increasingly therebelow due to wear and grinding.

The improved bed knife 38 of this invention comprises an elongated body39 preferably having a flat, planar lower face 40 and a flat, planar,rearward face 41 normal thereto, adapted to be firmly seated in asuitable recess 42 at the forward extremity of the bed 21 in theconventional manner.

The web-supporting upper face 44 of the bed knife 38 inclines upwardlyand forwardly from the rearward, upper edge 45 to the forward cuttingedge portion 49, whereby the edge 45 is slightly below plane 35, forexample .062 inch. The cutting edge 46 is at a predeter mined spaceddistance above plane 35, for example .062 inch and the plane 35intersects the mid width of the upper face 44 of the bed knife. The edge45 is thus depressed below the plane of the upper face 36 of bed 21 sothat stock advancing thereover cannot strike the edge due to dimensionalerrors in the bed knife recess, or seat, 42. Preferably, in a bed knifeof the proportions illustrated, the angle of inclination is about threeand one half degrees, since a greater inclination would guide andsupport the leading edge 47 of the plastic web 7.5 to an undesirablyhigh level and adversely aflect the out.

For example, in a bed knife approximately twenty-two inches long, twoand one fourth inches wide and .812 inch thick at the rearward face, theforward face may be about .937 inch thick. The forward cutting edgeportion 49 of the upper face 44 may thus be ground down for sharpening adistance of .062 inch before reaching the level of the plane 35.

Preferably the forward cutting edge portion 49 of the upper face 44 isinitially parallel to the lower face 40 in a plane parallel to the plane35 when the knife 38 is seated in recess 42. Grinding for sharpening isalso in a plane parallel to plane 35 so that the portion 49, which maybe of a width initially equal to twice the depth of the teeth 50,becomes increasingly wider with each grinding, but remains a minorportion of the width of the knife with the major portion 51, inclined asspecified.

The toothed forward face 53 of the bed knife 38, is angularly disposedat an acute angle to the upper face 44, the faces 49 and 53 meeting atthe sharp, toothed, cutting edge 46.

A web 25 which is self supporting will, thus not be in contact with theflat, horizontal forward portion 49 of the upper face 44, there being anangular space 54 therebetween. Such a space does not adversely affectcutting by the fly knives. Non self-supporting, limp webs will besupported on the portion 49, however, and it will be obvious that, ifdesired, the leading edge 47 of the web can be pressed downwardlyflatwise against portion 49 by a suitable roll or other mechanicalpresser device. The cutting edge 46 of bed knife 33 is in a radial planedesignated by the dotted line 55, the plane 55 being angularly inadvance of the radial plane 35.

The body 39 of bed knife 38 includes at least one, and preferably tworows 56 and 57 of staggered countersunk bolt holes such as 58 and 59,each bolt hole extending from upper face 44 to lower face 40. The rows56 and 57 are at a spaced distance in rear of the toothed forward face46, in the major portion 51 of upper face 44 so that repeated grindingsof the forward face portion 49 will not overlap, or reach the boltholes. Suitable threaded bolts 61 are provided to detachably aflix thebed knife 38 in its recess 42 in the bed 21 of machine 20.

In the particular embodiment shown, the width of the cutting edgeportion 49 is about one quarter of an inch initially and the forwardcutting face 46 is inclined away about eight degrees from a linetangential to the fly knife path at the cutting edge.

The improved bed knife 38 has been found to eliminate the flutter of theplastic web material which occurs with conventional bed knives regroundwith a recess in the conventional manner.

We claim:

1. In a pelletizing machine of the type having fly .knives, each with atoothed cutting edge, rotating unidirectionally about an axis in acylindrical path, a bed supporting a web of sheet material, 'to bepelletized, in

a horizontal plane generally radial to said axis and propelling meansfeeding said web along said bed into the path of said fly knives thecombination of:

a stationary bed knife, fixed at the extremity of said bed, said bedknife having a toothed forward cutting edge and forward faceintermeshing at close clear ance with the toothed cutting edges of saidfly knives, and 7 a web-supporting, upper face on said bed knife, saidface inclining upwardly and forwardly from the radial horizontal planeof said bed to a plane substantially spaced above said radial plane saidforward cutting edge and guiding the leading edge of said web into thecircular path of said fly knives at a radial plane angularlysubstantially in advance of the radial plane of said bed.

2.. A bed knife as specified in claim 1 wherein:

said web-supporting upper face inclines upwardly and forwardly at anangle of about three and one half degrees from the radial plane of saidbed.

3. A bed knife as specified in claim 1 wherein:

said web-supporting upper face inclines upwardly and forwardly, relativeto the radial plane of said bed, from the rearward edge thereof for themajor portion of the distance to the forward cutting edge thereof butthe remaining minor portion of said face is in a plane parallel to theradial plane of said bed.

4. A bed knife for use in a rotary, fly-knife type,

pelletizing machine having a web supporting bed in a generallyhorizontal plane, said bed knife comprising:

an elongated knife body having a lower face adapted to be seated at theforward extremity of the bed 4 V ofsaid machine, ata spaced distancefrom the path of the cutting edges of the fly knives thereof;

a web supporting upper face on said body inclining upwardly andforwardly from the rearward edge to proximate the forward cutting edgethereof, said face being intersected, in about mid width, by theplane ofsaid bed, and

a toothed, forward face on said body angularly disposed at an acuteangle to said upper face, said faces meeting at a sharp, toothed,forward cutting edge.

5. A bed knife as specified in claim 4 wherein:

the forward portion of said inclined upper face, for a depth slightlygreater than the depth of said teeth, is in a plane parallel to theplane of said lower face and parallel to -the plane of said bed.

6. A bed knife as specified in claim 4 wherein:

said body includes a longitudinally extending row of bolt holes, eachextending from said upper face to said lower face, at a spaced distancein rear of said toothed forward face; 7

whereby the cutting edge portion of said inclined upper face may beground down to sharpen said edges without overlapping said bolt holes.

7. A bed knife as specified in claim 1 wherein:

said web supporting upper face is about two and one quarter inches inwidth and is inclined at an angle of about three and one half degreesrelative to the plane of said bed whereby the forward cutting edge ofsaid knife is about .062 inches above, and the rearward edge of saidknife is about .062 inches below, the level of the plane of said bed.

References Cited by the Examiner UNITED STATES PATENTS 2,782,853 2/1957Hefielfinger 33 3s0 2,812,815 11/1957 Quinsey et a1 83906 X FOREIGNPATENTS 544,605 2/1932 Germany.

WILLIAM w. DYER, JR., Primary Examiner.

L. B. TAYLOR, Assistant Examiner.

1. IN A PELLETIZING MACHINE OF THE TYPE HAVING FLY KNIVES, EACH WITH ATOOTHED CUTTING EDGE, ROTATING UNIDIRECTIONALLY ABOUT AN AXIS IN ACYLINDRICAL PATH, A BED SUPPORTING A WEB OF SHEET MATERIAL, TO BEPELLETIZED, IN A HORIZONTAL PLANE GENERALLY RADIAL TO SAID AXIS ANDPROPELLING MEANS FEEDING SAID WEB ALONG SAID BED INTO THE PATH OF SAIDFLY KNIVES THE COMBINATION OF: A STATIONARY BED KNIFE, FIXED AT THEEXTREMITY OF SAID BED, SAID BED KNIFE HAVING A TOOTHED FORWARD CUTTINGEDGE AND FORWARD FACE INTERMESHING AT CLOSE CLEARANCE WITH THE TOOTHEDCUTTING EDGES OF SAID FLY KNIVES, AND A WEB-SUPPORTING, UPPER FACE ONSAID BED KNIFE, SAID FACE INCLINING UPWARDLY AND FORWARDLY FROM THERADIAL HORIZONTAL PLANE OF SAID BED TO A PLANE SUBSTANTIALLY SPACEDABOVE SAID RADIAL PLANE SAID FORWARD CUTTING EDGE AND GUIDING THELEADING EDGE OF SAID WEB INTO THE CIRCULAR PATH OF SAID FLY KNIVES AT ARADIAL PLANE ANGULARLY SUBSTANTIALLY IN ADVANCE OF THE RADIAL PLANE OFSAID BED.